reciprocity and program zl_zin ??
 

The program zl_zin calculates a Zload from a known Zin. It would seem that given
a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so?

Is there a program that will calculate Zin from a known Zload?

Thanks - Dan kb0qil

reciprocity and program zl_zin ??
 

dansawyeror wrote:
The program zl_zin calculates a Zload from a known Zin. It would seem
that given a symmetrical feedline that Zin and Zload should be mirrors.
Why is that not so?

I'm not sure what you mean by "mirrors". But the relationship between
Zin and Zload is dictated by the way transmission lines transform
impedances. A better question is, why should it be anything else?

A series inductor is symmetrical, is it not? Suppose you have a series
inductor with impedance +j10 ohms in a box. Connect it to a load of 50 +
j0 ohms. Looking into the input of the series inductor, you see 50 + j10
ohms. Now put a load of 50 + j10 ohms at the output instead of 50 + j0.
Are you saying you expect to see 50 + j0 at the input? Why?

Is there a program that will calculate Zin from a known Zload?

Hopefully someone else will be able to answer that.

Roy Lewallen, W7EL

reciprocity and program zl_zin ??
 

On Fri, 23 Dec 2005 15:46:16 -0800, dansawyeror
wrote:

The program zl_zin calculates a Zload from a known Zin. It would seem that given
a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so?

Line loss.


Is there a program that will calculate Zin from a known Zload?

http://www.vk1od.net/tl/tllce.php will work both ways, Zin from Zload,
and Zload from Zin.

Owen

Thanks - Dan kb0qil
--

reciprocity and program zl_zin ??
 

Roy,

Well the intuition was correct, however the problem is one level more complex.
The Smith chart shows the following approximate 'mirror' relationships for j=0:

Load Input Measurement
20 125
25 100
35 71
10 250
50 50

It is a "log" mirror centered on 50 Ohms. The mirror relationship holds for j /=
0, however the calculation is more complex. - Dan

Roy Lewallen wrote:
dansawyeror wrote:

The program zl_zin calculates a Zload from a known Zin. It would seem
that given a symmetrical feedline that Zin and Zload should be
mirrors. Why is that not so?


I'm not sure what you mean by "mirrors". But the relationship between
Zin and Zload is dictated by the way transmission lines transform
impedances. A better question is, why should it be anything else?

A series inductor is symmetrical, is it not? Suppose you have a series
inductor with impedance +j10 ohms in a box. Connect it to a load of 50 +
j0 ohms. Looking into the input of the series inductor, you see 50 + j10
ohms. Now put a load of 50 + j10 ohms at the output instead of 50 + j0.
Are you saying you expect to see 50 + j0 at the input? Why?

Is there a program that will calculate Zin from a known Zload?


Hopefully someone else will be able to answer that.

Roy Lewallen, W7EL

reciprocity and program zl_zin ??
 

On Fri, 23 Dec 2005 15:46:16 -0800, dansawyeror
wrote:

The program zl_zin calculates a Zload from a known Zin. It would seem that given
a symmetrical feedline that Zin and Zload should be mirrors. Why is that not so?

Line loss (if I understand your question correctly)


Is there a program that will calculate Zin from a known Zload?

http://www.vk1od.net/tl/tllce.php will work both ways, Zin from Zload,
and Zload from Zin.

Owen

Thanks - Dan kb0qil
--

reciprocity and program zl_zin ??
 

Is there a program that will calculate Zin from a known Zload?

==========================================

Yes, from the same place you obtained program ZL_ZIN.

For coax lines use program COAXPAIR.
For balanced twin lines use programs RJELINE3 or 4.

These programs are to professional standards, 1% accuracy or better,
covering the frequency range from audio to UHF.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

reciprocity and program zl_zin ??
 

On Fri, 23 Dec 2005 16:10:01 -0800, Roy Lewallen
wrote:

dansawyeror wrote:
The program zl_zin calculates a Zload from a known Zin. It would seem
that given a symmetrical feedline that Zin and Zload should be mirrors.
Why is that not so?

I'm not sure what you mean by "mirrors". But the relationship between
Zin and Zload is dictated by the way transmission lines transform
impedances. A better question is, why should it be anything else?

Roy, I also wasn't quite sure of the concept of *symmetry* and
*mirror* as used by Dan.

I made the assumption (perhaps incorrectly) that the transformation is
symmetrical for an integral number of half waves of lossless
transmission line. Impedances might be seen to "mirror" (if mirror
means an exact copy) for an integral number of half waves of lossless
line.

Having made that assumption, loss introduces errors to the
"mirroring", and line lengths other than an integral number of quarter
waves aren't symmetrical in that sense.

Having read Dan's further comments, it seems he thought any length of
real line was symmetric as an impedance transformer. It might be that
you can swap A and B ends in a circuit and obtain the same behaviour,
but you can't swap Zload and Zin in the general case.

Dan, the terms you have used don't have common usage in this context,
and confuse the issue.

Owen
--

reciprocity and program zl_zin ??
 

dansawyeror wrote:
Roy,

Well the intuition was correct, however the problem is one level more
complex. The Smith chart shows the following approximate 'mirror'
relationships for j=0:

Load Input Measurement
20 125
25 100
35 71
10 250
50 50

It is a "log" mirror centered on 50 Ohms. The mirror relationship holds
for j /= 0, however the calculation is more complex. - Dan

Well, yes, you can find specific relationships for various special cases
of load impedance and line length, particularly if you assume zero loss.
But only the appropriate equations, derived from basic principles, will
give you the correct relationship in the general case. Be wary of
oversimplification.

Roy Lewallen, W7EL

reciprocity and program zl_zin ??
 

On Sat, 24 Dec 2005 01:35:01 GMT, Owen Duffy wrote:


I made the assumption (perhaps incorrectly) that the transformation is
symmetrical for an integral number of half waves of lossless
transmission line. Impedances might be seen to "mirror" (if mirror
means an exact copy) for an integral number of half waves of lossless
line.


That should have read:

I made the assumption (perhaps incorrectly) that the transformation is
symmetrical for an integral number of *quarter* waves of lossless
transmission line. Impedances might be seen to "mirror" (if mirror
means an exact copy) for an integral number of half waves of lossless
line.

Owen
--

reciprocity and program zl_zin ??
 

Thanks,

Can you explain "transmission performance". Is it as measured and the source,
Zin? What is the range of Reflection Coeff? Is it a percentage? Is refl. coeff.
angle measured at Input?

Thanks, Dan

Reg Edwards wrote:
Is there a program that will calculate Zin from a known Zload?


==========================================

Yes, from the same place you obtained program ZL_ZIN.

For coax lines use program COAXPAIR.
For balanced twin lines use programs RJELINE3 or 4.

These programs are to professional standards, 1% accuracy or better,
covering the frequency range from audio to UHF.
----
.................................................. .........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. .........

reciprocity and program zl_zin ??
 

"dansawyeror" wrote in message
...
Thanks,

Can you explain "transmission performance". Is it as measured and
the source,
Zin? What is the range of Reflection Coeff? Is it a percentage? Is
refl. coeff.
angle measured at Input?

===================================
"Transmission performance" is just a descriptive term relating to how
well a line works compared with what is expected from it. It is not
measurable. It is a way of referring to the very many different
characteristics / properties / attributes of anything which performs.
It can be good, poor, better, worse, etc., etc.

The "reflection coefficient" is a dimension-less ratio, the
mathematical relationship between line Zo and the line terminating
impedance Zt.

RC = ( Zt - Zo ) / ( Zt + Zo ).

In general, both Zt and Zo are complex quantities and therefore RC
possesses both magnitude and a phase angle.

The magnitude can be anywhere between 0 and 1+Sqrt(2) although only in
very exceptional circumstances will it exceed 1.0 It is never
expressed as a percentage.

The phase angle can lie in any of the 4 quadrants of a circle. i.e.,
it can have an angle anywhere between 0 and 360 degrees. When
performing calculations it is more comvenient to refer to the angle as
lying between -180 and +180 degrees.

It can be referred to any point along a line. The angle, as in a
vector, rotates as the reference point moves away from the termination
towards the generator.

As you are probably aware, RC is closely related to SWR. SWR can be
calculated from RC. But RC cannot be calculated from SWR. This is
because RC conveys twice the amount of information as SWR. When
calculating SWR from RC half the information is lost. The angle of
SWR disappears.

SWR is the end of the line! Whether SWR is measured or calculated you
can't go much further.

But SWR / RC is a fascinating subject.
----
Reg, G4FGQ.